Platisil ods c18 column

Simultaneous determination of antiretroviral drugs was performed using an HPLC-MS/MS system. Briefly, the reconstituted solution (10 μL) was injected into the 1200 HPLC system (Agilent, Waldbronn, Germany) and separated with a Platisil ODS C18 column (5 μm, 150 mm×4.6 mm; Dikma), protected by a C18 guard cartridge (5 μm, 10 mm×4.6 mm; Dikma). A mixture of methanol and 0.004 mol/L ammonium acetate in tri-distilled water (95:5, v/v) was used as the mobile phase, which was filtered through a 0.22 μm microporous membrane and ultrasonic-processed for 10 min after preparation. The column oven temperature was 40 ± 1°C, and the flow rate was 300 μL/min.
MS detection was performed with a 3200 QTRAP tandem mass spectrometer (ABI, Foster City, CA, USA), equipped with an ESI source operating in MRM-positive mode. Liquid nitrogen was gasified as the nebulizing gas. The symmetric heaters were at 400°C and the ion spray voltage was 4500 V. Curtain gas was maintained at 10 psig, collision gas at medium (approximately 7 psig), and ion source gas 1 and gas 2 at 40 psig. The precursor ions and product ions of all analytes and their optimum conditions were re-optimized based on our previous studies^{18 , 19} (see Table S1 and Fig S1 in Supplemental Materials) and the dwell time was 100 ms.